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January 1, 2010 volume 1
Standards for HVAC Clarified
The new (2008) California Building Energy Efficiency
Standards will go into effect on January 1, 2010. The
new Standards make a distinction between two types of
change-out situations
1) New or Replacement Space Conditioning Systems
include a completely new or replacement duct system,
and a new or replacement air handler unit.
2) Altered Space Conditioning Systems
Utilize
the pre-existing duct system when installing or
replacing some or all of the system components, such
as the air handler unit, outdoor condensing unit,
cooling or heating coil, or furnace heat exchanger.
The new Standards require that change-outs must be
tested to ensure they meet the Home Energy Rating
System (HERS) requirements in some climate zones as
shown in the table below.
3) Duct Sealing and Testing
In
Climate Zones 2 and 9-16 the duct sealing and testing
rules that began in 2005 remain in effect. There are
no changes to the allowable leakage rates or to which
of the climate zones must meet the requirements.
However, there is a change that eliminates the Table
8-3 “Alternatives to Duct Sealing” options from the
Residential Compliance Manual. The Result is that
installation of higher efficiency equipment is no
longer an available alternative to meeting the HERS
Duct Seal Test requirements.
4)
Refrigerant Charge (RC) Verification
In Climate
Zone 2 and 8-15, for Altered space conditioning systems
and also for New or Replacement space conditioning
systems, Refrigerant Charge Verification by
third-Party HERS rater is required either for each unit or
by sampling as is done in the current standard.
The
installing contractor must measure the refrigerant charge,
make any necessary corrections, then complete an
Installation Certificate form that must be posted at the
job site for use at final inspection. A third party HERS
rater must also verify the RC. In order to achieve a valid
RC Verification, the system must meet or exceed a minimum
Cooling Coil Airflow (CCA) rate of 300 cfm per nominal ton
of capacity by direct measurement or by the temperature
split method. This airflow requirement is less stringent
than airflow rate required for Cooling Coil Airflow and
Fan Watt Draw Testing Described below.
If
the system fails to meet the minimum airflow requirement,
the HVAC contractor must modify the duct system or air
handler equipment in order to increase the system
airflow.
Installers of New or Replacement space conditioning
systems should consider reevaluating the duct system
design prior to installation of the ducts (Using an
industry recognized duct design method such as ACCA manual
D) rather that simply replacing an old poorly designed
duct system with "like for like" to end up with a brand
new poorly designed duct system. Installers of
Altered space conditioning systems need to consider
modification to the existing ducts to improve the airflow.
Modifications such as enlarging the return duct and return
grille, may be sufficient.
Installers of New or Replacement space conditioning
systems (with new duct systems) must install
Saturation Temperature Measurement Sensors (STMS).
STMS make
It is possible for HERS raters to verify RC without
attaching gauges to the refrigerant lines.
Installers
of
altered space conditioning systems
do not have to install the STMS. Both altered and
new
or replacement space conditioning systems require
Temperature Measurement Access Holes (TMAH). A
non-intrusive alternative to RC that is introduced by
the new Energy Standards is the Charge Indicator
Display (CID). If a CID is installed at the factory or
in the field by the HVAC contractor, STMS and TMAH are
not required.
5)
Temperature Measurement Access Holes (TMAH)
TMAH
are 5/16” holes that the installing contactor must
drill – one in the supply plenum and one in the return
plenum. The exact locations are specified in the
Energy Commission document Reference Residential
Appendices in section RA3.2. Watch for classes and
training on installation of the TMAH.
6)
Saturation Temperature Measurement Sensors (STMS)
STMS
are Type K thermocouples that are attached permanently
– one to the evaporator coil and one to the condenser
coil. The mini plug at the end of the thermocouple
wire is plugged
into a handheld digital thermometer to read the coil
saturation temperature. This direct measurement of the
temperature of the saturated region of the coil is an
alternative to use of gauges for determining the coil
saturation temperature readings needed for the
refrigerant charge verification. The STMS may be
installed at the factory or in the field by the HVAC
contractor. Watch for classes and training on
installation of the STMS.
7)
Charge Indicator Display (CID)
CID
is a new technology that is not yet commercially
available, but when these devices become available,
this will be a non-intrusive alternative to performing
RC verification for the HERS rater. However the HVAC
contractor will still need to perform RC verification
at the time of the installation of the system. Watch
for more information about the CID when it becomes
available.
8)
Thermostatic Expansion Valves (TXV)
TXV are no longer qualify
for an automatic “pass” for HERS refrigerant charge
verification. Systems with TXVs need to be tested for
correct sub-cooling to verify refrigerant charge, and
tested for superheat to ensure the TXVs are mounted
and operating as designed.
9) Cooling Coil Airflow (CCA) and Fan Watt Draw (FWD)
FWD
testing in Climate Zones 10-15, new or replacement
space conditioning systems (with new duct systems)
must meet the CCA and FWD requirements. The airflow
and watt draw measurements must be made
simultaneously, and the results from the measurements
are used to calculate a Watt per CFM value for the
test result.
The air handler must deliver an air-flow
of
at least 350 CFM per nominal ton of capacity in order
to pass, and the calculated result must be less than
or equal to 0.58 Watts per CFM of measured airflow in
order to pass the test. The installing contractor must
measure the CCA and FWD, make any necessary
corrections, then complete an Installation Certificate
form that must be posted at the job site for use at
final inspection. A third party HERS rater must also
verify the CCA and FWD.
If the system fails to meet
the minimum airflow, the HVAC contractor must modify
the system ducts and/or air handler equipment in order
to increase the system airflow.
Duct system
improvements such as those mentioned above for meeting
the minimum airflow for refrigerant charge
verification are applicable to CCA and FWD.
Additionally, installation of a more efficient air
handler unit may be a solution to meeting the required
Watt per
CFM.
In some situations (but not all)
an air handler with a brushless permanent magnet motor
might provide reduced fan Watt draw. If the problem is
low air flow due to high static pressure, a higher
efficiency motor by itself will probably not solve the
problem. A good duct design, carefully installed, is
highly recommended, and may be the lowest cost
solution. Airflow measurement
10)
Air Flow Measurement
Air Flow Measurement Procedures are described in the
Energy Commission document, Reference Residential
Appendices in section RA3.3. There are three
acceptable methods:
1) Flow Capture Hood at the return grille (s).
2)
Flow Grid Device at the return grille (s) or other
point where all the fan airflow shall flow through the
flow grid.
3)
Plenum Pressure Matching Procedure uses the same duct
pressurization and Flow measurement device (fan
flow-meter) as is used to measure
duct leakage. This procedure has
been simplified for the new Standards to allow connection
of the fan flow-meter at the return grille in the same way
as
for the duct leakage test. This
change makes it possible to test both the duct leakage and
the airflow with the Same setup, which may be a time
saver.
Watch for classes and training
on this method.
11) Fan
Watt Draw (FWD) Testing
Fan
Watt Draw Measurement must be done with a true Power
meter device that measures voltage and amperage
simultaneously and reports the true power value. True
power meters are available in both plug-in and clamp-on
configurations. Voltage and amperage can be taken
separately, but their product is Volt Amps or “Apparent
Watt Draw.” True watt draw is the product of the voltage,
amperage, AND power factor |
